The invention relates to determining, recording, and processing the geometry of a railroad track, determining, recording, and processing the geometry of a vehicle traveling on the track, and using such information to control operation of one or more vehicles on the track and to effectuate maintenance of the track. It finds particular application in conjunction with using the geometric information to improve operational safety and overall efficiency (e.g., fuel efficiency, vehicle wheel wear, and track wear) and will be described with particular reference thereto. It will be appreciated, however, that the invention is also amendable to other like applications.
Heretofore, track geometry systems determine and record geometric parameters of railroad tracks used by vehicles (e.g., railroad cars and locomotives) and generate an inspection or work notice for a section of track if the parameters are outside a predetermined range. Each vehicle includes a body secured to a truck, which rides on the track. Conventional systems use a combination of inertial and contact sensors to indirectly measure and quantify the geometry of the track. More specifically, an inertial system mounted on the truck senses motion of the truck in relation to the track. A plurality of transducers measure relative motion of the truck in relation to the track.
One drawback of conventional systems is that a significant number of errors occur from transducer failures. Furthermore, significant errors also result from a lack of direct measurements of the required quantities in a real-time manner.
Furthermore, conventional inertial systems typically use off-the-shelf gyroscopes and other components, which are designed for military and aviation applications. Such off-the-shelf components are designed for high rates of inertial change found in military and aircraft applications. Therefore, components used in conventional systems are poorly suited for the relatively low amplitude and slow varying signals seen in railroad applications. Consequently, conventional systems compromise accuracy in railroad applications.
The current technology in locomotive traction control is based on an average North American curve of approximately 2.5 degrees. If real-time rail geometry data, including current curvature and superelevation and cross-level, can be provided, then the drive system can be optimized for current track conditions, resulting in maximum efficiency.
The relationship between the tractive force that drives the locomotive, or other type of vehicle, forward on a rail is expressed by the following equation:FTraction=FNormal*u                where u is the coefficient of static friction and FNormal is the normal force at the rail/wheel interface.        
Balance speed is the optimum speed of the vehicle at which the resultant force vector is normal to the rail. By maintaining a vehicle at its balanced speed point, FNormal is maximized. Accordingly, FTraction is also maximized when the vehicle is operated at its balanced speed. Furthermore, by maintaining the drive wheels at the highest point of static friction while operating at the balanced speed, the maximum amount of available tractive force (FTraction) is achieved.
A small change in the velocity (V) through a curve results in significant changes in the lateral (centripetal) forces, as shown in the following equation:FLateral=Mass*Alateral,where Alateral=(1/Rcurve)*V^2
No current system provides the information necessary to compute the balance speed and therefore determine the most efficient operation of the train. Additionally, no current device or system allows for the inspection of rail track structures, determination of track geometric conditions, and identification of track defects in real-time. Furthermore, no current device or system communicates such information to other locomotive control mechanisms (e.g., locomotive control computers) in real-time allowing for real-time locomotive control.